Mass spectrometry (MS) identification algorithm
Inventors
Sadowski, Charles S. • Andersson, Greger • Judge, Kevin
Assignees
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Publication Number
US-10041915-B2
Publication Date
2018-08-07
Expiration Date
Abstract
A system includes a gas chromatograph configured to determine experimental chromatographic data including retention times associated with samples. The system also includes a mass spectrometer configured to determine experimental mass spectral data associated with samples. The mass spectrometer can include a quadrupole field ion trap that uses a non-classical detection technique. The system determines a retention index for an unknown sample based upon retention times for a calibration sample and the unknown sample, and identifies reference mass spectral data using the retention index. The reference mass spectral data can include spectra measured using a classical detection technique. The system can compare the experimental mass spectral data to the reference mass spectral data using one or more comparison metrics, such as a percent fragment match and/or a variance match. A score can be determined to identify the unknown sample using one or more of the metrics.
Core Innovation
The problem addressed is identifying an unknown sample using GC-MS by comparing non-classical experimental mass spectra to reference mass spectral data. The approach relies on chromatographic retention time data from a calibration sample and the unknown sample, and uses that retention time information to compute a retention index for the unknown sample.
A GC-MS system determines experimental chromatographic data that includes a first retention time associated with the calibration sample and a second retention time associated with the unknown sample. Based upon these retention times, the processor determines a retention index for the unknown sample and identifies a subset of a plurality of database entries included in an electronic database comprising reference mass spectral data using the retention index.
The filtered subset is used in the subsequent comparison step against the experimental mass spectral data for the unknown sample. The processor compares the experimental mass spectral data to the subset of database entries to identify the unknown sample, and the document further describes the possibility of ion-chemistry adjustments and combined score evaluation using additional metrics.
After identification, the system initiates an alert when the identification of the unknown sample is associated with a sample of interest.
Claims Coverage
The independent claims cover three implementations of the same inventive identification workflow: a GC-MS system, a computer-implemented method, and a computer-readable storage medium. Across the independent claims, the inventive core consists of computing a retention index from calibration and unknown retention times, using that retention index to select a subset of reference database entries, and comparing experimental mass spectral data to the subset to identify the unknown sample, with an alert associated with a sample of interest.
Retention-index-based electronic database pre-filtering for unknown identification
Determine a retention index for the unknown sample based upon the first retention time associated with the calibration sample and the second retention time associated with the unknown sample, identify a subset of a plurality of database entries included in an electronic database comprising reference mass spectral data using the retention index determined for the unknown sample, and compare the experimental mass spectral data to the subset to identify the unknown sample.
Alert when identified unknown sample is associated with a sample of interest
Initiate an alert when the identification of the unknown sample is associated with a sample of interest.
Across the independent claims, the inventive coverage is directed to deriving a retention index from calibration and unknown retention times, selecting a subset of reference mass spectral database entries using the retention index, and comparing experimental mass spectral data to that subset to identify the unknown sample, with an alert when the identified sample is associated with a sample of interest.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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